The study of group polarization began with an unpublished 1961 Master’s thesis by MIT student James Stoner, who observed the so-called "risky shift", meaning that a group’s decisions are riskier than the average of the individual decisions of members before the group met. Group polarization has been widely considered as a fundamental group decision-making process and was well-established, but remained non-obvious and puzzling because its mechanisms were not fully understood.
Social comparison approaches, sometimes called interpersonal comparison, were based on social psychological views of self-perception and the drive of individuals to appear socially desirable. The second major mechanism is informational influence, which is also sometimes referred to as persuasive argument theory, or PAT. PAT holds that individual choices are determined by individuals weighing remembered pro and con arguments. These arguments are then applied to possible choices, and the most positive is selected. As a mechanism for polarization, group discussion shifts the weight of evidence as each individual exposes their pro and con arguments, giving each other new arguments and increasing the stock of pro arguments in favor of the group tendency, and con arguments against the group tendency.